Electronic control device

ABSTRACT

A first output voltage of a constant-voltage power supply is applied as a reference voltage of a multi-channel A-to-D converter and a monitor signal obtained by smoothing the first output voltage by a first power-supply filter is inputted as an input signal voltage. A micro-processor periodically writes digital conversion data of the monitor signal into shift registers to calculate a maximum deviation using a maximum value and a minimum value of the latest predetermined number of data, and determines a power-supply abnormality when the maximum deviation exceeds a predetermined threshold value.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electronic control device equippedwith a micro-processor and a multi-channel A-to-D converter both fedfrom a constant-voltage power supply, and more particularly, to anelectronic control device improved so as to constantly monitor thepresence or absence of a power-supply abnormality in a constant-voltagepower supply.

2. Description of the Related Art

As in-vehicle electronic control devices for automobile, there is avoltage monitor device equipped with a micro-processor that monitors avariation of a digital conversion value by monitoring a power-supplyvoltage to be fed to a reference power-supply terminal of an A-to-Dconverter.

For example, JP-A-09-027749 (Patent Document 1) (see FIG. 1) discloses avoltage monitor device including a circuit (resistor 1 and zener diode2) that generates a constant voltage Vz from an analog input voltage(for example, Vcc) to be monitored in such a manner that the constantvoltage Vz has a lower value than the analog input voltage, an A-to-Dconverter 3, and further a CPU 4 that monitors a variation of a digitalvalue outputted from the A-to-D converter 3 connected inversely to anormal use of an A-to-D converter in such a manner that the analog inputvoltage to be monitored is given to a reference voltage terminal 3 s andthe constant voltage Vz is given to an analog input terminal 3 a.According to this voltage monitor device, it becomes possible to providea device that not only makes it possible to monitor a voltage variationaccurately, but also makes it easy to change a comparative voltage.

Also, JP-A-2009-022152 (Patent Document 2) (see FIG. 14) discloses aconstant-voltage power supply for in-vehicle electronic control devicehaving multiple types of stabilized output voltages and configured toperform comprehensive abnormality processing by detecting the presenceor absence of an abnormality in each output voltage. In order to performcomprehensive abnormality processing by detecting the presence orabsence of an abnormality in each output voltage, the constant-voltagepower supply generates an output voltage Vad of 5 V as a high-accuratelow-capacity power supply, an output voltage Vif of 5 V as alow-accurate high-capacity power supply, and an output voltage Vcp of3.3 V as a low-accurate high-capacity power supply. Further, theconstant-voltage power supply generates at least one of an outputvoltage Vup of 2.8 V as a low-accurate low-capacity power supply and anoutput voltage Vsb of 3.3 V as a high-accurate low-capacity powersupply. A determination signal input circuit compares a divided voltageof the output voltage Vif, a divided voltage of the output voltage Vcp,a divided voltage of the output voltage Vup, and a divided voltage ofthe output voltage Vsb in reference, for example, to a divided voltageof the output voltage Vad. The determination signal input circuit thenprocesses the comparison results by logic synthesis and inputs relativevoltage information ER2, ER3, ER4, and ER5 into the micro-processor. Themicro-processor makes a comprehensive determination including thecomparative reference voltage on the basis of the relative voltageinformation and notifies an abnormality or saves abnormality occurrenceinformation. The reference numerals and the signs used above are thoseused in respective Patent Documents.

-   [Patent Document 1] JP-A-09-027749 (Abstract and FIG. 1)-   [Patent Document 2] JP-A-2009-022152 (Abstract and FIG. 14)

According to the voltage monitor device disclosed in Patent Document 1,by configuring in such a manner that the analog input voltage to bemonitored is given to the reference voltage terminal and the constantvoltage (reference voltage) is given to the analog input terminal, theconstant voltage used as the reference voltage can take a lower valuethan the analog input voltage to be monitored. Hence, the constantvoltage can be generated easily from the analog input voltage (forexample, power-supply voltage Vcc) to be monitored using a simplecircuit, such as a zener diode.

However, voltage characteristics vary from one zener diode to anotherand the reference voltage to be monitored varies in a similar manner.Hence, the obtained result is too uncertain to make a determination asto which one is correct. In order to make the obtained result certain,temperature characteristics have to be corrected beforehand so as toaccommodate a change of the environmental temperature in a broad rangeby performing an initial calibration corresponding to characteristics ofan actual zener diode. Hence, there is a problem that the constantvoltage (reference voltage) is by no means inexpensive.

According to the in-vehicle electronic control device disclosed inPatent Document 2, an output voltage of the constant-voltagepower-supply circuit having a high degree of output voltage accuracyamong multiple constant-voltage power-supply circuits is used as thecomparative reference voltage. The presence or absence of an individualabnormality is detected by a band comparison as to whether outputvoltages of multiple constant-voltage power-supply circuits are withinan allowable variation range. Hence, when the high-accurate voltage usedas the comparative reference has a pulsation variation, a relativecomparison becomes difficult. In such a case, there arises a problemthat not only an accurate abnormality determination cannot be made, butalso magnitude of the pulsation variation cannot be understoodquantitatively.

SUMMARY OF THE INVENTION

A first object of the invention is to obtain an electronic controldevice of an inexpensive configuration that does not require ahigh-accurate reference voltage used as a determination reference orinitial calibration processing thereof in order to determine anabnormality in an output voltage of a constant-voltage power supply.

A second object of the invention is to obtain an electronic controldevice of an inexpensive configuration capable of detecting a pulsationcomponent of an output voltage quantitatively in order to detectgeneration of a voltage ripple as a sign of a power-supply abnormality.

An electronic control device according to an aspect of the inventionincludes: a constant-voltage power supply having a constant-voltagecontrol circuit portion that distributes and feeds or divides and feedsa first output voltage or a second output voltage among multiple outputvoltages, each of which is fed to a different subject, by an inputpower-supply voltage fed from an outside power supply; and a maincontrol circuit portion having a multi-channel A-to-D converter fed bythe first output voltage having a highest degree of accuracy among themultiple output voltages, and a micro-processor, a program memory, and aRAM memory fed by the second output voltage, all of which cooperate todrive an electronic load group under control in response to an operationcondition of a switch sensor group and an analog sensor group.

The multi-channel A-to-D converter generates a digital output inproportion to a ratio of a reference voltage applied to a referencevoltage terminal and an input signal voltage and, when the ratio is 1,generates a maximum digital output, 2^(n)−1, according to an n-bitresolution, where n is a predetermined number.

Also, the first output voltage is applied to the reference voltageterminal as a reference voltage and a smoothed power-supply monitorsignal to be used as a power-supply monitor voltage is inputted as oneof input signal voltages of the multi-channel A-to-D converter, or avoltage is applied to the reference voltage terminal from the firstoutput voltage as the reference voltage by suppressing a pulsationcomponent via a reference power-supply filter and an unsmoothedpower-supply monitor signal to be used as the power-supply monitorvoltage is inputted as one of the input signal voltages of themulti-channel A-to-D converter.

The smoothed power-supply monitor signal is a smoothed voltage obtainedfrom a divided voltage of the first output voltage by suppressing apulsation component via the first power-supply filter, and a dividingratio of the divided voltage is set so that the smoothed voltage takes avalue not greater than a lowest value of a pulsation of the referencevoltage.

The unsmoothed power-supply monitor signal is a divided voltage of thefirst output voltage and a dividing ratio of the divided voltage is setso that the divided voltage takes a value not greater than the lowestvalue of the pulsation of the reference voltage.

The micro-processor cooperates with the program memory and periodicallyinputs a digital conversion value of the smoothed power-supply monitorsignal or the unsmoothed power-supply monitor signal into a shiftregister formed of the RAM memory to calculate a maximum deviation,which is a deviation between a maximum value and a minimum value of alatest predetermined number of digital conversion values, and determinesan abnormality in the constant-voltage power supply in a case where thecalculated maximum deviation exceeds a predetermined threshold value.

According to the electronic control device of the invention configuredas above, the first output voltage, which is an output voltage havingthe highest degree of accuracy among the multiple output voltages by theconstant-voltage power supply or a divided voltage thereof, is appliedto one of the reference voltage terminal and an analog input terminal ofthe multi-channel A-to-D converter, and a smoothed voltage or a dividedvoltage of the first output voltage is applied to the other. A pulsationdeviation voltage of the first output voltage is calculated from thedigital conversion values obtained by making one of the applied voltagesas a smoothed voltage and the other as an unsmoothed voltage todetermine the presence or absence of an abnormality in theconstant-voltage power supply.

In order to determine whether accuracy of a high-accurate output voltageis appropriate or not, a comparative reference voltage with a higherdegree of accuracy is required and it becomes difficult to obtain acomparative reference voltage at a low cost. However, given the factthat a pulsation variation is normally generated in an output voltagewhen an abnormality occurs in the constant-voltage power supply that wasverifies to be normal by a first article inspection at the time ofshipment, by detecting the occurrence of this pulsation variation, itbecomes possible to detect the occurrence of an abnormality in theconstant-voltage power supply.

Accordingly, by performing digital conversion according to the referencevoltage or the power-supply monitor voltage including a pulsationcomponent and the power-supply monitor voltage or the reference voltagewhose pulsation component is smoothed, the obtained digital conversionvalue pulsates, so that a pulsation component of the first outputvoltage can be detected easily in the form of a digital value. Hence,there can be achieved an advantage that the occurrence of an abnormalitycan be detected quickly by constantly monitoring the presence or absenceof an abnormality in the constant-voltage power supply by comparisonwith a predetermined threshold value.

Also, regarding the reference power-supply voltage and the power-supplymonitor voltage, one is generated by smoothing the other and there is noneed to prepare a new high-accurate comparative reference voltage.Hence, there can be achieved an advantage that an abnormality can bedetermined accurately by an inexpensive configuration.

The foregoing and other objects, features, aspects, and advantages ofthe present invention will become more apparent from the followingdetailed description of the present invention when taken conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing an overall configuration of an electroniccontrol device according to a first embodiment of the invention;

FIG. 2 is a partial detailed circuit diagram of the electronic controldevice according to the first embodiment of the invention;

FIG. 3 is a characteristic diagram of an abnormal voltage waveform ofthe electronic control device according to the first embodiment of theinvention;

FIG. 4 is a flowchart depicting an operation of the electronic controldevice according to the first embodiment of the invention;

FIG. 5 is a view showing an overall configuration of an electroniccontrol device according to a second embodiment of the invention;

FIG. 6 is a partial detailed circuit diagram of the electronic controldevice according to the second embodiment of the invention;

FIG. 7 is a flowchart depicting an operation of the electronic controldevice according to the second embodiment of the invention;

FIG. 8 is a view showing an overall configuration of an electroniccontrol device according to a third embodiment of the invention;

FIG. 9 is a partial detailed circuit diagram of the electronic controldevice according to the third embodiment of the invention; and

FIG. 10 is a flowchart depicting an operation of the electronic controldevice according to the third embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of an electronic control device ofthe invention will be described using the drawings. Descriptions will begiven by labeling same or equivalent portions with same referencenumerals in the respective drawings.

First Embodiment

Firstly, a configuration of an electronic control device according to afirst embodiment of the invention will be described in detail using anoverall configuration view of FIG. 1 and a partial detailed circuitdiagram of FIG. 2.

Referring to FIG. 1, an input power-supply voltage Vb is applied to anelectronic control device 100A from an outside power supply 101, whichis, for example, an in-vehicle battery, via an output contact 102 a of apower-supply relay. Also, even when the output contact 102 a is open, anauxiliary power-supply voltage Vbb for micro-power is directly appliedto the electronic control device 100A from the outside power supply 101.

An exciting coil 102 b of the power-supply relay is energized when anenergization transistor 112 a is brought into conduction and driven viaan unillustrated base circuit by a power-supply switch signal PWS thatreacts to a power-supply switch 103. The energization transistor 112 ais controlled by the electronic control device 100A so that even whenthe power-supply switch 103 is opened, the energization transistor 112 acontinues to conduct via an energization resistor 112 b by a self-holdcommand signal DRV generated by a micro-processor 121 described belowand is de-energized with a delay of a predetermined time.

A first analog sensor 104, a second analog sensor 105, a switch sensorgroup 106, and an electrical load group 107 are connected to theelectronic control device 100A. It should be noted that an analog sensorgroup 108 is formed of the first analog sensor 104 that operates on afirst output voltage Vad described below as a power supply, a detectionsignal voltage of which as a sensor varies in proportion to a value ofthe first output voltage Vad, for example, like a potentiometer, and thesecond analog sensor 105 that operates on the input power-supply voltageVb or the first output voltage Vad as a power supply, a detection signalvoltage of which as a sensor is not influenced by a pulsation variationof the first output voltage Vad due to a high-accurate constant-voltagecontrol circuit portion or constant-current control circuit portionincluded in the sensor.

A constant-voltage power supply 110 built in the electronic controldevice 100A generates first, second, and third output voltages Vad, Vcp,and Vif, which are stabilized voltages stepped-down from the inputpower-supply voltage Vb, and also generates a fourth output voltage Vup,which is a stabilized voltage stepped-down from the auxiliarypower-supply voltage Vbb.

A main control circuit portion 120A is formed of a micro-processor 121,a program memory 122A, a computation processing RAM memory 123, amulti-channel A-to-D converter 124A, an input interface circuit 125, andan output interface circuit 126. These components are interconnected bya data bus.

The program memory 122A cooperates with the micro-processor 121 and ispre-installed with a control program run to realize a calibrationprocessing portion 403 b, an abnormality determination portion 408, andan abnormality determination subject update portion 409 described belowwith reference to FIG. 4.

The RAM memory 123 contains shift registers SRGi and SFTj describedbelow and is fed from the second and fourth output voltages Vcp and Vupvia diodes 113 a and 113 b, respectively. Power-supply monitor signalsMa1, Mb2, and Mb3 are inputted into the multi-channel A-to-D converter124A from a power-supply monitor circuit 130A described below withreference to FIG. 2. Also, a first analog signal A1k is inputted fromthe first analog sensor 104 via a noise filter 140 and a second analogsignal A2j is inputted from the second analog sensor 105 via a noisefilter 150.

ON and OFF signals are inputted into the input interface circuit 125from the switch sensor group 106 via a preceding-stage input interfacecircuit 160. The preceding-stage input interface circuit 160 operates onthe input power-supply voltage Vb and is formed of a conversion circuitat a signal voltage level and a noise filter circuit. The electricalload group 107 is connected to the output interface circuit 126 via asubsequent-stage output interface circuit 170. The subsequent-stageoutput interface circuit 170 operates on the input power-supply voltageVb and is formed of a power transistor circuit that performs conversionat a signal voltage level.

The first output voltage Vad is a high-accurate low-capacity powersupply, for example, of DC 5 V±20 mV/20 mA and feeds a part of themulti-channel A-to-D converter 124A, the noise filters 140 and 150, andthe first and second analog sensors 104 and 105. It should be noted,however, that a buffer amplifier 114 is connected in series to feedcircuits for the first and second analog sensors 104 and 105 as asafeguard against a short circuit, and a part of the second analogsensor 105 operates on the input power-supply voltage Vb.

The second output voltage Vcp is a low-accurate high-capacity powersupply, for example, of DC 3.3 V±0.3 V/500 mA and feeds themicro-processor 121, the program memory 122A, and the RAM memory 123.

The third output voltage Vif is a low-accurate high-capacity powersupply, for example, of DC 5 V±0.2 V/200 mA and feeds the inputinterface circuit 125 and the output interface circuit 126.

The fourth output voltage Vup is a low-accurate low-capacity powersupply, for example, of DC 3.3 V±0.3 V/20 mA and feeds the RAM memory123 when the output contact 102 a of the power-supply relay is open.These output voltages are divided and fed separately from unillustratedmultiple constant-voltage control circuit portions provided in theconstant-voltage power supply 110. The first output voltage Vad and thethird output voltage Vif are same rated voltages at different degrees ofoutput voltage accuracy. Hence, by setting the output voltage accuracyto a high degree, these output voltages can be distributed and fed froma single constant-voltage control circuit portion.

Also, in a case where the micro-processor 121 is a low-capacity memoryoperating at a low speed, DC 5 V is used as the second output voltageVcp. In this case, the first output voltage Vad, the second outputvoltage Vcp, and the third output voltage Vif can be distributed and fedfrom a single constant-voltage control circuit portion.

Referring to FIG. 2, the first output voltage Vad is applied intact tothe multi-channel A-to-D converter 124A as a power-supply voltage Vccand a reference voltage Vref thereof. Also, the smoothed power-supplymonitor signal Ma1, the second power-supply monitor signal Mb2, and thethird power-supply monitor signal Mb3 generated by the power-supplymonitor circuit 130A, and the first analog signal A1k and the secondanalog signal A2j outputted from the noise filters 140 and 150,respectively, are inputted into the multi-channel A-to-D converter 124Aas input signals thereof.

The smoothed power-supply monitor signal Ma1 is a signal obtained fromthe first output voltage Vad via dividing resistors 115 a and 116 a anda first power-supply filter 119. The first power-supply filter 119 isformed of a smoothing resistor 117 and a smoothing capacitor 118.

The second output voltage Vcp is connected intact as the secondpower-supply monitor signal Mb2. The third power-supply monitor signalMb3 is a signal obtained from the third output voltage Vif via dividingresistors 115 c and 116 c.

The first analog signal A1k includes multiple analog signals obtainedfrom the first analog sensor 104 via the noise filter 140. The noisefilter 140 is formed of a bypass capacitor 142 to block a foreignhigh-frequency noise, an input resistor 141, and an output-end capacitor143.

The second analog signal A2j includes multiple analog signals obtainedfrom the second analog sensor 105 via the noise filter 150. The noisefilter 150 is formed of a bypass capacitor 152 to block a foreignhigh-frequency noise, an input resistor 151, and an output-end capacitor153. The multi-channel A-to-D converter 124A generates a digital outputin proportion to a ratio of the reference voltage Vref applied to thereference voltage terminal with respect to an input signal voltage Vin,such as the smoothed power-supply monitor signal Ma1, the secondpower-supply monitor signal Mb2, the third power-supply monitor signalMb3, the first analog signal A1k, and the second analog signal A2j,Vin/Vref. When Vin/Vref=1, the multi-channel A-to-D converter 124Agenerates a full-scale digital output, Dout=2^(n)−1, according to ann-bit resolution, where n is a predetermined number. Hence, given a10-bit resolution, then we obtain Dout=1023. Accordingly, when thereference voltage Vref is DC 5 V, 5 mV can be identified as a minimumunit of the input signal voltage Vin.

FIG. 3 is a characteristic diagram of an abnormal voltage waveform ofthe electronic control device 100A. Referring to FIG. 3, the ordinate isused for an output voltage of the first output voltage Vad during theoccurrence of an abnormality, and the abscissa is used for an elapsedtime. It is understood from this abnormality characteristic waveformthat the first output voltage Vad during the occurrence of anabnormality includes a pulsation component having a pulsation frequencyof 50 KHz and a pulsation amplitude of ±70 mV.

The first output voltage Vad in a normal state maintains accuracy of DC5 V±20 mV and is a stable low-amplitude low-frequency output voltagehaving a pulsation component of ±5 mV or less and a pulsation frequencyof several Hz or lower.

As has been described, an output voltage waveform of theconstant-voltage power supply 110 is a low-amplitude low-frequencypulsation output voltage in a normal state. However, the pulsationamplitude increases with a degree of the abnormal state and there is atendency that the pulsation frequency becomes higher with an increase ofthe pulsation amplitude.

Meanwhile, a conversion required time for the multi-channel A-to-Dconverter 124A to convert one input signal voltage Vin to a digital formis, for example, 3 μsec, and digital conversion accuracy is deterioratedas the pulsation frequency becomes higher.

However, because the pulsation amplitude is also increased when thepulsation frequency is high, the multi-channel A-to-D converter 124Awith a resolution of 5 mV can detect an abnormality occurring state in areliable manner.

The noise filters 140 and 150 provided to input circuits of the firstand second analog sensors 104 and 105, respectively, include the bypasscapacitors 142 and 152, respectively, which not only suppress a noisesignal of tens Hz to several KHz or higher generated in the analog inputcircuits, but also suppress a foreign high-frequency noise in a band ofseveral MHz to tens MHz. A noise suppressing effect of a noise filtercan be enhanced by increasing a smoothing time constant (that is, bylowering a break frequency) to the extent possible. However, on theother hand, responsivity as a sensor is deteriorated when the smoothingtime constant is increased excessively (that is, when the breakfrequency is lowered excessively). Hence, a noise filter having asmoothing time constant increased (the break frequency lowered) to theextent possible within an allowable range of the responsivity as asensor is adopted herein. Accordingly, in the case of the noise filter140 for the first analog sensor 104, a low-pass filter having a firstbreak frequency, for example, of 20 Hz is adopted and the same appliesto the noise filter 150 for the second analog sensor 105.

A filter constant of the first power-supply filter 119 is to smooth apulsation component of tens Hz to tens KHz or higher, which arepulsation frequencies when the first output voltage Vad is in anabnormal state, and the first power-supply filter 119 is a low-passfilter having a second break frequency, for example, of 10 Hz. Thepurpose of this configuration is to detect an abnormality quickly when apulsation component is generated in the first output voltage Vad. Hence,it is crucial that at least the smoothing time constant of the noisefilter 140 is smaller than the smoothing time constant of the firstpower-supply filter 119 and the first power-supply filter 119outperforms the noise filter 140 in terms of the smoothingcharacteristics.

The electronic control device 100A of the first embodiment is configuredas described above, and an operation and a function will now bedescribed in detail according to the flowchart of FIG. 4 depicting theoperation.

Firstly, referring to FIG. 1 and FIG. 2, when the power-supply switch103 is closed and the output contact 102 a of the power-supply relay isclosed, the constant-voltage power supply 110 having one or more thanone constant-voltage control circuit portions distributes and feeds ordivides and feeds the first output voltage Vad, the second outputvoltage Vcp, or the third output voltage Vif, each of which is fed to adifferent subject, by the input power-supply voltage Vb fed from theoutside power supply 101.

The micro-processor 121 starts to operate when the second output voltageVcp rises and drives the electrical load group 107 under control inresponse to an operation state of the switch sensor group 106 and theanalog sensor group 108 in cooperation with the program memory 122A andthe multi-channel A-to-D converter 124A. It should be noted that thefirst output voltage Vad is applied intact to the power-supply terminaland the reference voltage terminal of the multi-channel A-to-D converter124A.

Herein, the smoothed power-supply monitor signal Ma1 is obtained bysmoothing the first output voltage Vad by the first power-supply filter119. Because the reference voltage Vref of the multi-channel A-to-Dconverter 124A is the first output voltage Vad itself, when the firstoutput voltage Vad is normal, the digital conversion value of thesmoothed power-supply monitor signal Ma1 takes a constant value inproportion to a dividing ratio of the dividing resistors 115 a and 116a. However, when the first output voltage Vad becomes abnormal and thepulsation component is generated, the reference voltage Vref pulsateswhereas the digital conversion value of the smoothed power-supplymonitor signal Ma1 undergoes increased or reduced pulsation because thesmoothed power-supply monitor signal Ma1 is smoothed by the firstpower-supply filter 119 and a pulsation thereof is suppressed.

As will be described below with reference to FIG. 4, the micro-processor121 determines the presence or absence of an abnormality in the firstoutput voltage Vad by detecting this pulsation amplitude. It should benoted that a dividing ratio of the dividing resistors 115 a and 116 a isset so that a smoothed output voltage by the smoothed power-supplymonitor signal Ma1 takes a value not greater than a minimum value of thefirst output voltage Vad that pulsates.

The second and third power-supply monitor signals Mb2 and Mb3 arepower-supply monitor inputs to determine the presence or absence of anabnormality in the low-accurate second and third output voltages Vcp andVif, respectively, in reference to the high-accurate first outputvoltage Vad operating normally. As will be described below withreference to FIG. 4, the micro-processor 121 determines the presence orabsence of an abnormality in the second and third output voltages Vcpand Vif by monitoring average values and the pulsation amplitudes of thesecond and third power-supply monitor signals Mb2 and Mb3, respectively.

When the reference voltage Vref is normal or even when it is pulsatingat a low frequency, the first analog signal A1k itself pulsates inproportion to a pulsation of the first output voltage Vad as long as thefirst analog signal A1k is in a low frequency region where the firstanalog signal A1k is not influenced by the noise filter 140. Hence, thedigital conversion value does not pulsate and can take a value inproportion to a dividing ratio by the first analog sensor 104, which isa potentiometer. When the pulsation frequency of the first outputvoltage Vad becomes higher, the first analog signal A1k is smoothed bythe noise filter 140 whereas the reference voltage Vref is unsmoothed.Hence, the digital conversion value of the first analog signal A1kundergoes increased or reduced pulsation and cannot take an exactdividing ratio. It should be noted, however, that under theseconditions, an abnormality determination is made in advance bymonitoring the smoothed power-supply monitor signal Ma1.

A signal voltage as a sensor can be obtained from the second analogsignal A2j independently of a variation of the first output voltage Vad.There is, however, a problem that the digital conversion value thereofvaries in inverse proportion to the reference voltage Vref when thereference voltage Vref of the multi-channel A-t-D converter 124A varies.To overcome this problem, a digital conversion value from which apulsation component is removed is obtained in this embodiment bycalculating a moving average value of the digital conversion values aswill be described below with reference to FIG. 4.

Referring to FIG. 4, Step 400 is a step in which the micro-processor 121starts to perform analog signal processing periodically in cycles of,for example, at least 10 msec. or shorter.

Subsequent Step 401 is a step in which a content of a buffer memory BFM,which is provided in the multi-channel A-to-D converter 124A and inwhich digital conversion values of various input signal voltages Vin arestored, is read out and transferred to a predetermined region in the RAMmemory 123.

Subsequent Step 402 is a step in which the digital conversion values ofthe smoothed power-supply monitor signal Ma1, the second power-supplymonitor signal Mb2, and the third power-supply monitor signal Mb3 arestored, respectively, in first through third FIFO tables formed of shiftregisters SRGi=SRG0, SRG2, and SRG3, and the digital conversion valuesof the second analog signal A2j (j=1, 2, and so on) are stored inmultiple FIFO tables formed of shift registers SFTj=SFT1, SFT2, and soon. For example, up to sixteen 10-bit digital conversion values arestored in one FIFO table and once sixteen conversion values are stored,a new conversion value is stored by deleting the oldest data.

Subsequent Step 403 a is a step in which a moving average value iscalculated for each of the latest predetermined numbers of the digitalconversion values stored in the respective shift registers SRG2 and SRG3in Step 402 by dividing a sum of each shift register by the number ofadditions.

Subsequent Step 403 b is a step in which a moving average value iscalculated for each of the latest predetermined numbers of the digitalconversion values stored in the respective shift registers SFT1, SFT2,and so on in Step 402 by dividing a sum of each shift register by thenumber of additions. This step corresponds to a calibration processingportion to remove a pulsation component from the digital conversionvalue for the second analog signal A2j.

Subsequent Step 404 is a determination step in which a determination ismade as to whether it is abnormality determination timing or not.Herein, a determination of YES is made periodically in cycles, forexample, of 100 msec. or shorter at the beginning of or during theoperation, and advancement is then made to Step 405. When theabnormality determination is not to be made, a determination of NO ismade and advancement is made to Step 409. Step 405 is a step in which amaximum deviation, which is a deviation between a maximum value and aminimum value, is calculated for any one of the latest predeterminednumbers of the digital conversion values stored in the respective shiftregisters SRG0, SRG2, and SRG3 in Step 402. It is, however, preferableto perform probable statistical processing, by which actual maximumvalue and minimum value are discarded and a deviation between the secondlargest value and the second smallest value is found to be the maximumdeviation.

Subsequent Step 406 a is a determination step in which a determinationis made as to whether the maximum deviation calculated in Step 405 isexcessively large or not by comparison with a determination thresholdvalue of the maximum deviation set in advance for any one of the digitalconversion values of the smoothed power-supply monitor signal Ma1, thesecond power-supply monitor signal Mb2, and the third power-supplymonitor signal Mb3. When the maximum deviation is excessively large, adetermination of YES is made and advancement is made to Step 407 a andwhen the maximum deviation is normal, a determination of NO is made andadvancement is made to Step 406 b.

In Step 407 a, an abnormality is notified or at least abnormalityoccurrence information is written into a predetermined region of the RAMmemory 123, after which advancement is made to Step 406 b. Step 406 b isa determination step in which a determination is made as to whether themoving average value calculated in Step 403 a is excessively large orsmall by comparison with a target band value set in advance for any oneof the digital conversion values of the second power-supply monitorsignal Mb2 and the third power-supply monitor signal Mb3. When themoving average value is excessively large or small, a determination ofYES is made and advancement is made to Step 407 b. When the movingaverage value is normal, a determination of NO is made and advancementis made to Step 409. In Step 407 b, an abnormality is notified or atleast abnormality occurrence information is written into a predeterminedregion of the RAM memory 123, after which advancement is made to Step409. Herein, a step block 408 made up of Step 405 through Step 407 bcorresponds to an abnormality determination portion.

Step 409 is a step corresponding to an abnormality determination subjectupdate portion that sequentially updates the shift register numberselected in Step 405 from SRG0 to SRG2, from SGR2 to SGR3, and from SRG3to SRG0. In subsequent operation ending Step 410, the micro-processor121 runs another control program and returns to operation starting Step400 within a period, for example, of 10 msec. It should be noted thatStep 409 is a step to make an abnormality determination by limiting thesubject to one monitor signal voltage in the same computation cycle inorder to shorten an advancement time from Step 400 through Step 410.

As is obvious from the description above, an electronic control deviceof the first embodiment is the electronic control device 100A including:the constant-voltage power supply 110 having one or more than oneconstant-voltage control circuit portions that distributes and feeds ordivides and feeds the first output voltage Vad, the second outputvoltage Vcp, or the third output voltage Vif, each of which is fed to adifferent subject, by the input power-supply voltage Vb fed from theoutside power supply 101; and the main control circuit portion 120Ahaving the micro-processor 121, the program memory 122A, and the RAMmemory 123 fed by the second output voltage Vcp, and the multi-channelA-to-D converter 124A fed by the first output voltage Vad, all of whichcooperate to drive the electronic load group 107 under control inresponse to an operation condition of the switch sensor group 106 andthe analog sensor group 108.

The multi-channel A-to-D converter 124A generates a digital output inproportion to a ratio (Vin/Vref) of the reference voltage Vref appliedto the reference voltage terminal and an input signal voltage Vin and,when the ratio is 1, generates a maximum digital output, Dout=2^(n)−1,according to an n-bit resolution, where n is a predetermined number.

The first output voltage Vad having the highest degree of accuracy amongthe multiple output voltages is applied to the reference voltageterminal as the reference voltage Vref and the smoothed power-supplymonitor signal Ma1 to be used as the power-supply monitor voltage isinputted as one of the input signal voltages Vin of the multi-channelA-to-D converter 124A. The smoothed power-supply monitor signal Ma1 is asmoothed voltage obtained from a divided voltage of the first outputvoltage Vad by suppressing a pulsation component via the firstpower-supply filter 119, and a dividing ratio of the divided voltage isset so that the smoothed voltage takes a value not greater than a lowestvalue of a pulsation of the reference voltage Vref.

The micro-processor 121 cooperates with the program memory 122A andperiodically inputs a digital conversion value of the smoothedpower-supply monitor signal Ma1 into the shift register SRG0 formed ofthe RAM memory 123 to calculate a maximum deviation, which is adeviation between a maximum value and a minimum value of the latestpredetermined number of digital conversion values, and determines anabnormality in the constant-voltage power supply 110 in a case where thecalculated maximum deviation exceeds a predetermined threshold value.

Also, the electronic control device 100A may be configured in such amanner that one or both of the second output voltage Vcp and the thirdoutput voltage Vif are generated, respectively, by second and thirdconstant-voltage control circuit portions separated from theconstant-voltage control circuit portion that generates the first outputvoltage Vad.

Herein, as one of the input signal voltages Vin of the multi-channelA-to-D converter 124A, at least one of the second power-supply monitorsignal Mb2 and the third power-supply monitor signal Mb3 to be used asthe power-supply monitor voltage is inputted.

The second power-supply monitor signal Mb2 takes a value of the secondoutput voltage Vcp and a maximum value of the second output voltage Vcptakes a value not greater than a minimum value of the reference voltageVref.

The third power-supply monitor signal Mb3 is a divided voltage of thethird output voltage Vif that feeds the input interface circuit 125 andthe output interface circuit 126 provided to the main control circuitportion 120A, and a dividing ratio of the divided voltage is set so thata maximum value of the divided voltage takes a value not greater thanthe minimum value of the reference voltage Vref.

The micro-processor 121 cooperates with the program memory 122A andperiodically inputs the digital conversion value of one of the secondpower-supply monitor signal Mb2 and the third power-supply monitorsignal Mb3, respectively, into the shift registers SRG2 and SRG3 formedof the RAM memory 123 to calculate an average value of the latestpredetermined number of digital conversion values and a maximumdeviation, which is a deviation between a maximum value and a minimumvalue of the latest predetermined number of digital conversion values,and determines an abnormality in the constant-voltage power supply 110in a case where the calculated maximum deviation or both of thecalculated maximum deviation and the calculated average value exceedrespective predetermined threshold values or predetermined band values.

According to the second characteristics of the invention describedabove, of the multiple output voltages generated by the constant-voltagepower supply 110, the first output voltage Vad having the highest degreeof accuracy is inputted as the reference voltage Vref and at least oneof the second output voltage Vcp and the third output voltage Vif isinputted as the power-supply monitor voltage, and the presence orabsence of an abnormality in the constant-voltage power supply 110 isdetermined by calculating an average value or a maximum deviation of thepulsation of the digital conversion values of the power-supply monitorvoltage.

Hence, there is a characteristic that when the first output voltage Vadis determined as being normal, by inputting the first output voltage Vadhaving a high degree of accuracy as the reference voltage Vref, itbecomes possible to determine in a reliable manner the presence orabsence of an abnormality or the presence or absence of a pulsationvariation, which is a sign of the occurrence of an abnormality, inoutput voltages other than the first output voltage Vad.

The micro-processor 121 cooperates with the program memory 122A andperiodically makes an abnormality determination alternately for thesmoothed power-supply monitor signal Ma1 and at least one of the secondpower-supply monitor signal Mb2 and the third power-supply monitorsignal Mb3, so that more than one abnormality determination is not madein a same control flow.

According to the third characteristics of the invention described above,the abnormality determination processing for the power-supply monitorsignals of multiple types is performed in a time-dividing manner.

Hence, there is a characteristic that because more than one abnormalitydetermination is not made in the same computation cycle, it becomespossible to make an abnormality determination for multiple outputvoltages one by one by lessening a burden of high speed control on themicro-processor 121.

The first output voltage Vad having the highest degree of accuracy amongthe multiple output voltages is applied to the reference voltageterminal as the reference voltage Vref and the smoothed power-supplymonitor signal Ma1 to be used as the power-supply monitor voltage isinputted as one of the input signal voltages Vin of the multi-channelA-to-D converter 124A. The analog sensor group 108 includes the firstanalog sensor 104 that operates on the first output voltage Vad as apower supply, a detection signal voltage of which as a sensor varies inproportion to a value of the first output voltage Vad, and the secondanalog sensor 105 that operates on the input power-supply voltage Vb orthe first output voltage Vad as a power supply, a detection signalvoltage of which as a sensor is not influenced by a pulsation variationof the first output voltage Vad.

Input circuits of the first and second analog sensors 104 and 105include the bypass capacitors 142 and 152, respectively, that suppress aforeign high-frequency noise in a band of several MHz to tens MHz, andnoise filters 140 and 150 that suppress a noise component of tens Hz toseveral KHz or higher generated in the input circuits are connected tothe respective input circuits.

Of the noise filters 140 and 150, at least the noise filter 140connected to the first analog sensor 104 is a low-pass filter having afirst break frequency, whereas the first power-supply filter 119 is alow-pass filter that smoothes a pulsation component of tens Hz to tensKHz or higher, which are pulsation frequencies when the first outputvoltage Vad is in an abnormal state, and has a second break frequencylower than the first break frequency.

According to the fourth characteristics of the invention describedabove, the noise filters 140 and 150 not only to suppress a foreignsurge voltage but also to suppress a noise component generated in theinput circuits are connected to the input circuits of the analog sensorgroup 108. In order to suppress a pulsation component of the firstoutput voltage Vad, the noise filters 140 and 150 become effective in afrequency region higher than that of the power-supply filter.

Hence, there is a characteristic that while a pulsation frequency of thefirst output voltage Vad is low, the first analog signal A1k by thefirst analog sensor 104 varies in association with a variation of thefirst output voltage Vad even when a pulsation amplitude of the firstoutput voltage Vad or the center value thereof itself varies, and highaccurate digital conversion can be performed. In addition, when thefirst output voltage Vad changes to an abnormal state and a pulsationfrequency becomes higher, because the first analog signal A1k issmoothed by the noise filters 140, the first analog signal A1k no longervaries in association with the first output voltage Vad and digitalconversion accuracy is deteriorated. However, there is a characteristicthat the occurrence of an abnormality can be detected in this case bythe micro-processor 121 that monitors the smoothed power-supply monitorsignal.

Likewise, in the case of the second analog signal A2j by the secondanalog sensor 105, there is a characteristic that while the first outputvoltage Vad is in a normal state, even when the second analog signal A2jcontains a low-amplitude pulsation component allowed at low frequencies,the second analog signal A2j is converted into a digital form within anallowable error range. Also, the digital conversion accuracy of thesecond analog signal A2j deteriorates when the pulse amplitudeincreases. However, there is a characteristic that the occurrence of anabnormality can be detected by the micro-processor 121 in this case.

The micro-processor 121 cooperates with the program memory 122A andperiodically inputs a digital conversion value of the second analogsignal A2j, which is at least one of signals of the second analog sensor105, into the shift register SFTj formed of the RAM memory 123 tocalculate a moving average value, which is an average value of thelatest predetermined number of digital conversion values, and specifiesthe calculated moving average value as a digital conversion value forthe second analog signal A2j.

According to the fifth characteristics of the invention described above,when the second analog signal A2j by the second analog sensor 105, adetection signal voltage of which as a sensor is stable even when thevalue of the first output voltage Vad pulsates, is inputted as an inputsignal of the multi-channel A-to-D converter 124A operating on the firstoutput voltage Vad by the constant-voltage power supply 110 used as thereference voltage Vref, the moving average value of the digitalconversion values is specified as a digital conversion value for thesecond analog signal A2j.

Hence, there are characteristics that even when the digital conversionvalue is obtained by converting an input signal voltage not influencedby a variation of the first output voltage Vad into a digital formaccording to the reference voltage Vref including a pulsation componentand this digital conversion value pulsates, an exact digital conversionvalue can be obtained easily by calculating the moving average value ofthe digital conversion values.

Also, in the case of the first analog sensor 104, a detection signalvoltage of which as a sensor varies in proportion to a value of thefirst output voltage Vad, an exact digital conversion value can beobtained even when the reference voltage Vref of the multi-channelA-to-D converter 124A pulsates at a low frequency. Hence, there is acharacteristic that it is more advantageous when the analog sensor group108 includes a larger number of the first analog sensors 104.

Also, even with the second analog sensor 105, by applying calibrationprocessing only to those having a small detection signal voltage andrequiring a high-accurate digital conversion value, it becomes possibleto prevent a control burden from being applied excessively to themicro-processor 121.

Second Embodiment

A configuration of an electronic control device according to a secondembodiment of the invention, chiefly a difference from the firstembodiment above, will now be described in detail using an overallconfiguration view of FIG. 5 and a partial detailed circuit diagram ofFIG. 6. In the first embodiment above, the first output voltage Vad isapplied intact to the reference voltage terminal of the multi-channelA-to-D converter 124A and the smoothed power-supply monitor signal Ma1obtained by smoothing the first output voltage Vad by the firstpower-supply filter 119 is inputted as the input signal voltage Vin. Incontrast to this configuration, a main difference of the secondembodiment is that a voltage obtained by smoothing the first outputvoltage Vad by a reference power-supply filter 129 is applied to areference voltage terminal of a multi-channel A-to-D converter 124B andan unsmoothed power-supply monitor signal Mb1 obtained by dividing thefirst output voltage Vad is inputted as the input signal voltage Vin.Same reference numerals denote same or equivalent portions in therespective drawings.

Referring to FIG. 5, as in the first embodiment above, the outside powersupply 101, the output contact 102 a and the exciting coil 102 b of thepower-supply relay, the power-supply switch 103, the analog sensor group108 formed of the first analog sensor 104 and the second analog sensor105, the switch sensor group 106, and the electrical load group 107 areconnected to an electronic control device 100B, to which an inputpower-supply voltage Vb and an auxiliary power-supply voltage Vbb areapplied.

As in the first embodiment above, the constant-voltage power supply 110,the feeding diodes 113 a and 113 b, the buffer amplifier 114, a maincontrol circuit portion 120B, a power-supply monitor circuit 130Bdescribed below with reference to FIG. 6, the noise filters 140 and 150,the preceding-stage input interface circuit 160, and thesubsequent-stage output interface circuit 170 are provided in theelectronic control device 100B.

The main control circuit portion 120B is formed of the micro-processor121, a program memory 122B, the computation processing RAM memory 123, amulti-channel A-to-D converter 124B, the input interface circuit 125,and the output interface circuit 126. These components areinterconnected by a data bus. It should be noted that power is fed tothe reference voltage terminal of the multi-channel A-to-D converter124B from the first output voltage Vad via a reference power-supplyfilter 129 formed of a smoothing resistor 127 and a smoothing capacitor128.

The program memory 122B cooperates with the micro-processor 121 and ispre-installed with a control program run to realize an abnormalitydetermination portion 708 and an abnormality determination subjectupdate portion 709 described below with reference to FIG. 7. The RAMmemory 123 contains shift registers SRGi described below and is fed fromthe second and fourth output voltages Vcp and Vup via the diodes 113 aand 113 b, respectively.

An unsmoothed power-supply monitor signal Mb1 and second and thirdpower-supply monitor signals Mb2 and Mb3 are inputted into themulti-channel A-to-D converter 124B from a power-supply monitor circuit130B described below with reference to FIG. 6. Also, a first analogsignal A1k is inputted from the first analog sensor 104 via the noisefilter 140 and a second analog signal A2j is inputted from the secondanalog sensor 105 via the noise filter 150.

As with the case of FIG. 1, the constant-voltage power supply 110generating first through fourth output voltages feeds power fromunillustrated multiple constant-voltage control portions provided in theconstant-voltage power supply 110 by dividing the respective outputvoltages. The first output voltage Vad and the third output voltage Vifare same rated voltages at different degrees of output voltage accuracy.Hence, by setting the output voltage accuracy to a high degree, theseoutput voltages can be distributed and fed from a singleconstant-voltage control circuit portion. Also, in a case where themicro-processor 121 is a low-capacity memory operating at a low speed,DC 5 V is used as the second output voltage Vcp. In this case, the firstoutput voltage Vad, the second output voltage Vcp, and the third outputvoltage Vif can be distributed and fed from a single constant-voltagecontrol circuit portion.

Referring to FIG. 6, a voltage obtained by smoothing the first outputvoltage Vad by the reference power-supply filter 129 is applied to themulti-channel A-to-D converter 124B as the power-supply voltage Vcc andthe reference voltage Vref.

Also, the unsmoothed power-supply monitor signal Mb1, and the secondpower-supply monitor signal Mb2 and the third power-supply monitorsignal Mb3 described above with reference to FIG. 2, all of which aregenerated by the power-supply monitor circuit 130B, and the first analogsignal A1k and the second analog signal A2j outputted from the noisefilters 140 and 150, respectively, are connected to the multi-channelA-to-D converter 124B as input signals. Herein, the unsmoothedpower-supply monitor signal Mb1 is a signal obtained by dividing thefirst output voltage Vad using the dividing resistors 115 a and 116 a.

The noise filters 140 and 150 provided to input circuits of the firstand second analog sensors 104 and 105, respectively, include the bypasscapacitors 142 and 152, respectively, which not only suppress a noisesignal of tens Hz to several KHz or higher generated in the analog inputcircuits, but also suppress a foreign high-frequency noise in a band ofseveral MHz to tens MHz. As has been described in the first embodimentabove, a noise suppressing effect can be enhanced by increasing asmoothing time constant (that is, by lowering a break frequency) to theextent possible. However, on the other hand, responsivity as a sensor isdeteriorated when the smoothing time constant is increased excessively(that is, when the break frequency is lowered excessively). Hence, anoise filter having a smoothing time constant increased (that is, thebreak frequency lowered) to the extent possible within an allowablerange of the responsivity as a sensor is adopted for the noise filters140 and 150 herein. Accordingly, at least in the case of the noisefilters 140 for the first analog sensor 104, a low-pass filter having afirst break frequency, for example, of 20 Hz is adopted and the sameapplies to the noise filter 150.

On the contrary, a filter constant of the reference power-supply filter129 is to smooth a pulsation component of tens Hz to tens KHz or higher,which are pulsation frequencies when the first output voltage Vad is inan abnormal state, and the reference power-supply filter 129 is alow-pass filter having a break frequency as high as that of the noisefilter 140. This is crucial to maintain a high degree of digitalconversion accuracy by allowing the first analog signal A1k to pulsatein association with a pulsation of the reference voltage Vref smoothedby the reference power-supply filter 129 when a pulsation component isgenerated in the first output voltage Vad. Regarding filter constants ofthe same characteristics, a resistor and a capacitor forming thelow-pass filter vary from one to another. It is therefore sufficient forthese filters to establish a relation having an overlapped region suchthat a minimum value of the one having the larger smoothing timeconstant is equal to or less than the maximum value of the other havingthe smaller smoothing time constant.

The electronic control device 100B of the second embodiment isconfigured as above and an operation and a function will now bedescribed in detail according to the flowchart of FIG. 7 depicting theoperation. In FIG. 7, steps denoted by 400 s correspond to those denotedby 400 s in FIG. 4 and descriptions will be given herein to stepsdenoted by 700 s, which are different from those in FIG. 4.

Firstly, referring to FIG. 5 and FIG. 6, when the power-supply switch103 is closed and the output contact 102 a of the power-supply relay isclosed, the constant-voltage power supply 110 having one or more thanone constant-voltage control circuit portions distributes and feeds ordivides and feeds the first output voltage Vad, the second outputvoltage Vcp, or the third output voltage Vif, each of which is fed to adifferent subject, by the input power-supply voltage Vb fed from theoutside power supply 101.

The micro-processor 121 starts to operate when the second output voltageVcp rises and drives the electrical load group 107 under control inresponse to an operation state of the switch sensor group 106 and theanalog sensor group 108 in cooperation with the program memory 122B andthe multi-channel A-to-D converter 124B. It should be noted that avoltage obtained by smoothing the first output voltage Vad by thereference power-supply filter 129 is applied to the power-supplyterminal and the reference voltage terminal of the multi-channel A-to-Dconverter 124B.

Herein, the unsmoothed power-supply monitor signal Mb1 is a dividedvoltage of the first output voltage Vad. Because the reference voltageVref of the multi-channel A-to-D converter 124B is obtained by smoothingthe first output voltage Vad, when the first output voltage Vad isnormal, the digital conversion value of the unsmoothed power-supplymonitor signal Mb1 takes a constant value in proportion to a dividingratio of the dividing resistors 115 a and 116 a. However, when the firstoutput voltage Vad becomes abnormal and a pulsation component isgenerated, the pulsation of the reference voltage Vref is suppressedwhereas the unsmoothed power-supply monitor signal Mb1 pulsates. Hence,the digital conversion value of the unsmoothed power-supply monitorsignal Mb1 undergoes increased or decreased pulsation.

As will be described below with reference to FIG. 7, the micro-processor121 determines the presence or absence of an abnormality in the firstoutput voltage Vad by detecting this pulsation amplitude. It should benoted that a dividing ratio of the dividing resistors 115 a and 116 a isset so that a maximum value of the divided voltage by the unsmoothedpower-supply monitor signal Mb1 takes a value not greater than thereference voltage Vref whose pulsation is suppressed.

The second and third power-supply monitor signals Mb2 and Mb3 arepower-supply monitor inputs to determine the presence or absence of anabnormality in the low-accurate second and third output voltages Vcp andVif, respectively, in reference to the reference voltage Vref obtainedby smoothing the high-accurate first output voltage Vad operatingnormally by the reference power-supply filter 129. As will be describedbelow with reference to FIG. 7, the micro-processor 121 determines thepresence or absence of an abnormality in the second and third outputvoltages Vcp and Vif by monitoring average values and the pulsationamplitudes of the second and third power-supply monitor signals Mb2 andMb3, respectively.

When the first output voltage Vad is pulsating or even when the averagevalue varies, the first analog signal A1k itself varies in proportion toa variation of the first output voltage Vad, and moreover, the noisefilter 140 having the characteristics same as those of the referencepower-supply filter 129 is connected to the first analog signal A1k.Hence, the digital conversion value does not pulsate and can take avalue in proportion to a dividing ratio by the first analog sensor 104,which is a potentiometer.

It should be noted, however, that in a case where a noise filter havinga higher break frequency than the reference power-supply filter 129 isused for a part of the first analog signal A1k, the digital conversionvalue pulsates between this high brake frequency and the break frequencyof the reference power-supply filter 129. An abnormality determinationis made in this state by the unsmoothed power-supply monitor signal Mb1.

Contrary to this configuration, a signal voltage as a sensor can beobtained from the second analog signal A2j independently of a variationof the first output voltage Vad, and in a case where the average valueof the first output voltage Vad falls within a predetermined accuracyrange and a pulsation component is included, the reference voltage Vrefof the multi-channel A-to-D converter 124B is smoothed by the referencepower-supply filter 129. Hence, the calibration processing portion thatcalculates a moving average value of the digital conversion values asdescribed in Step 403 b of FIG. 4 is not necessary herein.

Referring to FIG. 7, Step 702 following Step 401 is a step in which thedigital conversion values of the unsmoothed power-supply monitor signalMb1, the second power-supply monitor signal Mb2, and the thirdpower-supply monitor signal Mb3 are stored in first through third FIFOtables formed of the shift registers SRGi=SRG1, SRG2, and SRG3,respectively.

Subsequent Step 403 a is a step in which a moving average value of thelatest predetermined number of the digital conversion values stored ineach of the shift registers SRG2 and SRG3 in Step 702 is calculated bydividing a sum of each shift register by the number of additions.Herein, subsequent Step 403 b is omitted and advancement is made to Step404.

Step 705 that functions when a determination of YES is made in Step 404is a step in which a maximum deviation, which is a deviation between themaximum value and the minimum value, is calculated for any one of thelatest predetermined number of the digital conversion values stored inthe respective shift registers SRG1, SRG2, and SRG3 in Step 702. It is,however, preferable to perform probable statistical processing, by whichactual maximum value and minimum value are discarded and a deviationbetween the second largest value and the second smallest value is foundto be the maximum deviation.

Subsequent Step 706 a is a determination step in which a determinationis made as to whether the maximum deviation calculated in Step 705 isexcessively large or not by comparison with a determination thresholdvalue of the maximum deviation set in advance for any one of the digitalconversion values of the unsmoothed power-supply monitor signal Mb1, thesecond power-supply monitor signal Mb2, and the third power-supplymonitor signal Mb3. When the maximum deviation is excessively large, adetermination of YES is made and advancement is made to Step 407 a. Whenthe maximum deviation is normal, a determination of NO is made andadvancement is made to Step 406 b. A step block 708 made up of Step 705through Step 407 b corresponds to an abnormality determination portion.

Step 709 that functions when a determination of NO is made in Step 404or Step 406 b or subsequent to Step 407 b is a step corresponding to anabnormal determination subject update portion that sequentially updatesthe shift register number selected in Step 705 from SRG1 to SRG2, fromSRG2 to SRG3, and from SRG3 to SRG1.

As is obvious from the description above, an electronic control deviceof the second embodiment is the electronic control device 100Bincluding: the constant-voltage power supply 110 having one or more thanone constant-voltage control circuit portions that distributes and feedsor divides and feeds the first output voltage Vad, the second outputvoltage Vcp, or the third output voltage Vif, each of which is fed to adifferent subject, by the input power-supply voltage Vb fed from theoutside power supply 101; and the main control circuit portion 120Bhaving the micro-processor 121, the program memory 122B, and the RAMmemory 123 fed by the second output voltage Vcp, and the multi-channelA-to-D converter 124B fed by the first output voltage Vad, all of whichcooperate to drive the electronic load group 107 under control inresponse to an operation condition of the switch sensor group 106 andthe analog sensor group 108.

The multi-channel A-to-D converter 124B generates a digital output inproportion to a ratio (Vin/Vref) of the reference voltage Vref appliedto the reference voltage terminal and the input signal voltage Vin and,when the ratio is 1, generates a maximum digital output, Dout=2^(n)−1,according to an n-bit resolution, where n is a predetermined number.

A voltage is applied to the reference voltage terminal from the firstoutput voltage Vad having the highest degree of accuracy among themultiple output voltages as the reference voltage Vref by suppressing apulsation component via the reference power-supply filter 129 and theunsmoothed power-supply monitor signal Mb1 to be used as thepower-supply monitor voltage is inputted as one of the input signalvoltages Vin of the multi-channel A-to-D converter 124B. The unsmoothedpower-supply monitor signal Mb1 is a divided voltage of the first outputvoltage Vad and a dividing ratio of the divided voltage is set so thatthe divided voltage takes a value not greater than a lowest value of thepulsation of the reference voltage Vref.

The micro-processor 121 cooperates with the program memory 122B andperiodically inputs a digital conversion value of the unsmoothedpower-supply monitor signal Mb1 into the shift register SRG1 formed ofthe RAM memory 123 to calculate a maximum deviation, which is adeviation between a maximum value and a minimum value of the latestpredetermined number of digital conversion values, and determines anabnormality in the constant-voltage power supply 110 in a case where thecalculated maximum deviation exceeds a predetermined threshold value.

Also, the electronic control device 100B may be configured in such amanner that one or both of the second output voltage Vcp and the thirdoutput voltage Vif are generated, respectively, by second and thirdconstant-voltage control circuit portions separated from theconstant-voltage control circuit portion that generates the first outputvoltage Vad.

As one of the input signal voltages Vin of the multi-channel A-to-Dconverter 124B, at least one of the second power-supply monitor signalMb2 and the third power-supply monitor signal Mb3 to be used as thepower-supply monitor voltage is inputted.

The second power-supply monitor signal Mb2 takes a value of the secondoutput voltage Vcp and a maximum value of the second output voltage Vcptakes a value not greater than a minimum value of the reference voltageVref. The third power-supply monitor signal Mb3 is a divided voltage ofthe third output voltage Vif that feeds the input interface circuit 125and the output interface circuit 126 provided to the main controlcircuit portion 120B, and a dividing ratio of the divided voltage is setso that a maximum value of the divided voltage takes a value not greaterthan the minimum value of the reference voltage Vref.

The micro-processor 121 cooperates with the program memory 122B andperiodically inputs the digital conversion value of one of the secondpower-supply monitor signal Mb2 and the third power-supply monitorsignal Mb3, respectively, into the shift registers SRG2 and SRG3 formedof the RAM memory 123 to calculate an average value of the latestpredetermined number of digital conversion values and a maximumdeviation, which is a deviation between a maximum value and a minimumvalue of the latest predetermined number of digital conversion values,and determines an abnormality in the constant-voltage power supply 110in a case where the calculated maximum deviation or both of thecalculated maximum deviation and the calculated average value exceedrespective predetermined threshold values or predetermined band values.

According to the second characteristics of the invention describedabove, of the multiple output voltages generated by the constant-voltagepower supply 110, a smoothed voltage of the first output voltage Vadhaving the highest degree of accuracy is inputted as the referencevoltage Vref and at least one of the second output voltage Vcp and thethird output voltage Vif is inputted as the power-supply monitorvoltage, so that the presence or absence of an abnormality in theconstant-voltage power supply 110 is determined by calculating anaverage value or a maximum deviation of the pulsation of the digitalconversion values of the power-supply monitor voltage.

Hence, there is a characteristic that in a case where the first outputvoltage Vad is determined as being normal, by inputting the first outputvoltage Vad having a high degree of accuracy as the reference voltageVref, it becomes possible to determine in a reliable manner the presenceor absence of an abnormality or the presence or absence of a pulsationvariation, which is a sign of the occurrence of an abnormality, inoutput voltages other than the first output voltage Vad.

The micro-processor 121 cooperates with the program memory 122B andperiodically makes an abnormality determination alternately for theunsmoothed power-supply monitor signal Mb1 and at least one of thesecond power-supply monitor signal Mb2 and the third power-supplymonitor signal Mb3, so that more than one abnormality determination isnot made in a same control flow.

According to the third characteristics of the invention described above,the abnormality determination processing for the power-supply monitorsignals of multiple types is performed in a time-dividing manner.

Hence, as in the first embodiment above, there is a characteristic thatbecause more than one abnormality determination is not made in the samecomputation cycle, it becomes possible to make an abnormalitydetermination for multiple output voltages one by one by lessening aburden of high speed control on the micro-processor 121.

A voltage is applied from the first output voltage Vad to the referencevoltage terminal as the reference voltage Vref by suppressing apulsation component via the reference power-supply filter 129, and theunsmoothed power-supply monitor signal Mb1 to be used as thepower-supply monitor voltage is inputted as one of the input signalvoltages Vin of the multi-channel A-to-D converter 124B.

The analog sensor group 108 includes the first analog sensor 104 thatoperates on the first output voltage Vad as a power supply, a detectionsignal voltage of which as a sensor varies in proportion to a value ofthe first output voltage Vad, and the second analog sensor 105 thatoperates on the input power-supply voltage Vb or the first outputvoltage Vad as a power supply, a detection signal voltage of which as asensor is not influenced by a pulsation variation of the first outputvoltage Vad.

Input circuits of the first and second analog sensors 104 and 105include the bypass capacitors 142 and 152, respectively, that suppress aforeign high-frequency noise in a band of several MHz to tens MHz, andthe noise filters 140 and 150 that suppress a noise component of tens Hzto several KHz or higher generated in the input circuits are connectedto the respective input circuits.

Of the noise filters 140 and 150, at least the noise filter 140connected to the first analog sensor 104 is a low-pass filter having afirst break frequency, whereas the reference power-supply filter 129 isa low-pass filter that smoothes a pulsation component of tens Hz to tensKHz or higher, which are pulsation frequencies when the first outputvoltage Vad is in an abnormal state, and has a break frequency as highas the first break frequency.

According to the sixth characteristics of the invention described above,the noise filters 140 and 150 not only to suppress a foreign surgevoltage but also to suppress a noise component generated in the inputcircuits are connected to the input circuits of the analog sensor group108. The noise filters 140 and 150 are filters having thecharacteristics same as those of the reference power-supply filter 129used for the reference voltage Vref.

Hence, there is a characteristic that while the first output voltage Vadis in a normal state, the first analog signal A1k by the first analogsensor 104 pulsates in association with a pulsation of the first outputvoltage Vad even when the first output voltage Vad pulsates at a lowfrequency and is further inputted into the multi-channel A-to-Dconverter 124B via the noise filters 140 having the characteristics sameas those of the reference power-supply filter 129, and highly accuratedigital conversion can be performed.

Likewise, in the case of the second analog signal A2j by the secondanalog sensor 105, there is a characteristic that while the first outputvoltage Vad is in a normal state, even when the second analog signal A2jcontains a low-amplitude pulsation component allowed at low frequencies,the second analog signal A2j is converted into a digital form within anallowable error range. Also, there is a characteristic that even whenthe pulsation frequency becomes higher, because the reference voltageVref is smoothed, the digital conversion accuracy of the second analogsignal A2j is not deteriorated unless the average value of the firstoutput voltage Vad varies.

Third Embodiment

A configuration of an electronic control device according to a thirdembodiment of the invention, chiefly a difference from the firstembodiment or the second embodiment above, will now be described indetail using an overall configuration view of FIG. 8 and a partialdetailed circuit diagram of FIG. 9. In the first embodiment above, thefirst output voltage Vad is applied intact to the reference voltageterminal of the multi-channel A-to-D converter 124A and the smoothedpower-supplied monitor signal Ma1 obtained by smoothing the first outputvoltage Vad by the first power-supply filter 119 is inputted as theinput signal voltage Vin. Also, in the second embodiment above, avoltage obtained by smoothing the first output voltage Vad by thereference power-supply filter 129 is applied to the reference voltageterminal of the multi-channel A-to-D converter 124B and the unsmoothedpower-supply monitor signal Mb1 obtained by dividing the first outputvoltage Vad is inputted as the input signal voltage Vin.

Contrary to these configurations, a difference of the third embodimentis that a multi-channel A-to-D converter 124C is formed of a pair of amulti-channel A-to-D converter 124A and a multi-channel A-to-D converter124B, which is a combination of the first embodiment and the secondembodiment above. Herein, same reference numerals denote same orequivalent portions in the respective drawings.

Referring to FIG. 8, as in the first embodiment or the second embodimentabove, the outside power supply 101, the output contact 102 a and theexciting coil 102 b of the power-supply relay, the power-supply switch103, the analog sensor group 108 formed of the first analog sensor 104and the second analog sensor 105, the switch sensor group 106, and theelectrical load group 107 are connected to an electronic control device100C, to which an input power-supply voltage Vb and an auxiliarypower-supply voltage Vbb are applied.

As in the first embodiment or the second embodiment above, theconstant-voltage power supply 110, the feeding diodes 113 a and 113 b,the buffer amplifier 114, a main control circuit portion 120C, apower-supply monitor circuit 130C described below with reference to FIG.9, the noise filters 140 and 150, the preceding-stage input interfacecircuit 160, and the subsequent-stage output interface circuit 170 areprovided in the electronic control device 100C.

The main control circuit portion 120C is formed of the micro-processor121, a program memory 122C, the computation processing RAM 123, amulti-channel A-to-D converter 124C, the input interface circuit 125,and the output interface circuit 126. These components areinterconnected by a data bus. It should be noted that the first outputvoltage Vad is applied intact to the reference voltage terminal of onemulti-channel A-to-D converter 124A forming the multi-channel A-to-Dconverter 124C as the reference voltage Vref, whereas the referencevoltage terminal of the other multi-channel A-to-D converter 124B is fedfrom the first output voltage Vad via the reference power-supply filter129 formed of the smoothing resistor 127 and the smoothing capacitor128.

The program memory 122C cooperates with the micro-processor 121 and ispre-installed with a control program run to realize an abnormalitydetermination portion 1008 and an abnormality determination subjectupdate portion 1009 described below with reference to FIG. 10. The RAMmemory 123 contains shift registers SRGi described below and is fed fromthe second and fourth output voltages Vcp and Vup via the diodes 113 aand 113 b, respectively. As in the first embodiment or the secondembodiment above, the constant-voltage power supply 110 generating firstthrough fourth output voltages feeds power from unillustrated multipleconstant-voltage control circuit portions provided in theconstant-voltage power supply 110 by dividing the respective outputvoltages. The first output voltage Vad and the third output voltage Vifare same rated voltages at different degrees of output voltage accuracy.Hence, by setting the output voltage accuracy to a high degree, theseoutput voltages can be distributed and fed from a singleconstant-voltage control circuit portion.

Also, in a case where the micro-processor 121 is a low-capacity memoryoperating at a low speed, DC 5 V is used as the second output voltageVcp. In this case, the first output voltage Vad, the second outputvoltage Vcp, and the third output voltage Vif can be distributed and fedfrom a single constant-voltage control circuit portion.

Referring to FIG. 9, the smoothed power-supply monitor signal Ma1described above with reference to FIG. 2 is inputted into themulti-channel A-to-D converter 124A from the power-supply monitorcircuit 130C, and the first analog signal A1k inputted via the noisefilter 140 is inputted therein from the first analog sensor 104.

The unsmoothed power-supply monitor signal Mb1, the second power-supplymonitor signal Mb2, and the third power-supply monitor signal Mb3described above with reference to FIG. 6 are inputted to themulti-channel A-to-D converter 124B from the power-supply monitorcircuit 130C, and the second analog signal A2j inputted via the noisefilter 150 is inputted therein from the second analog sensor 105.

The noise filters 140 and 150 provided to input circuits of the firstand second analog sensors 104 and 105, respectively, include the bypasscapacitors 142 and 152, respectively, which not only suppress a noisesignal of tens Hz to several KHz or higher generated in the analog inputcircuits, but also suppress a foreign high-frequency noise in a band ofseveral MHz to tens MHz as has been described above with reference toFIG. 2. At least in the case of the noise filter 140 for the firstanalog sensor 104, a low-pass filter having a first break frequency, forexample, of 20 Hz is adopted and the same applies to the noise filter150 for the second analog sensor 105.

A filter constant of the first power-supply filter 119 is to smooth apulsation component of tens Hz to tens KHz or higher, which arepulsation frequencies when the first output voltage Vad is in anabnormal state, and the first power-supply filter 119 is a low-passfilter having a second break frequency, for example, of 10 Hz.

On the contrary, a filter constant of the reference power-supply filter129 is to smooth a pulsation component of tens Hz to tens KHz or higher,which are pulsation frequencies when the first output voltage Vad is inan abnormal state, as with the case of FIG. 6, and the referencepower-supply filter 129 is a low-pass filter having a break frequency ashigh as that of the noise filter 150.

This is crucial to maintain a high degree of digital conversion accuracyby allowing the second analog signal A2j to pulsate in association witha pulsation of the reference voltage Vref smoothed by the referencepower-supply filter 129 when a pulsation component is generated in thefirst output voltage Vad. Regarding filter constants of the samecharacteristics, the characteristics of a resistor and a capacitorforming the low-pass filter vary from one to another. It is thereforesufficient for these filters to establish a relation having anoverlapped region such that a minimum value of the one having the largersmoothing time constant is equal to or less than the maximum value ofthe other having the smaller smoothing time constant.

The electronic control device 100C of the third embodiment is configuredas described above and an operation and a function will now be describedin detail according to the flowchart of FIG. 10 depicting the operation.In FIG. 10, steps denoted by 400 s correspond to those denoted by 400 sin FIG. 4 and descriptions will be given herein to steps denoted by 1000s, which are different from those in FIG. 4.

Firstly, referring to FIG. 8 and FIG. 9, when the power-supply switch103 is closed and the output contact 102 a of the power-supply relay isclosed, the constant-voltage power supply 110 having one or more thanone constant-voltage control circuit portions distributes and feeds ordivides and feeds the first output voltage Vad, the second outputvoltage Vcp, or the third output voltage Vif, each of which is fed to adifferent subject, by the input power-supply voltage Vb fed from theoutside power supply 101.

The micro-processor 121 starts to operate when the second output voltageVcp rises and drives the electrical load group 107 under control inresponse to an operation state of the switch sensor group 106 and theanalog sensor group 108 in cooperation with the program memory 122C andthe multi-channel A-to-D converter 124C.

The first output voltage Vad is applied to the reference voltageterminal of one multi-channel A-to-D converter 124A forming themulti-channel A-to-D converter 124C and the smoothed power-supplymonitor signal Ma1 is applied as a power-supply monitor signal.

An output voltage of the reference power-supply filter 129 is applied tothe reference voltage terminal of the other multi-channel A-to-Dconverter 124B, and the unsmoothed power-supply monitor signal Mb1 isapplied as the power-supply monitor signal. Hence, both of the digitalconversion values of the smoothed power-supply monitor signal Ma1 andthe unsmoothed power-supply monitor signal Mb1 are used as a monitorsignal for a double system used to extract a pulsation component of thefirst output voltage Vad. Herein, either the smoothed power-supplymonitor signal Ma1 or the unsmoothed power-supply monitor signal Mb1 canbe omitted.

Alternatively, the second and third power-supply monitor signals Mb2 andMb3 inputted into the multi-channel A-to-D converter 124B may beinputted into the multi-channel A-to-D converter 124A.

In a case where the second and third power-supply monitor signals Mb2and Mb3 are connected to the multi-channel A-to-D converter 124B as isshown in FIG. 9, there can be achieved an advantage as in the case ofFIG. 6 that a detection of the pulsation amplitudes of the second andthird power-supply monitor signals Mb2 and Mb3 is not influenced by apulsation variation of the first output voltage Vad.

In a case where the second and third power-supply monitor signals Mb2and Mb3 are inputted into the multi-channel A-to-D converter 124A, thereis a characteristic as in the case of FIG. 2 that a pulsation variationof the first output voltage Vad is added when the pulsation amplitudesof the second and third power-supply monitor signals Mb2 and Mb3 aredetected, so that a combined abnormality determination is madeindependently of on which part an abnormality is present.

Herein, the first analog signal A1k is inputted into the multi-channelA-to-D converter 124A as a measure, in the case of the first analogsensor 104, to effectively utilize the characteristics that the digitalconversion accuracy thereof is not influenced by a variation of theaverage value or the pulsation amplitude of the first output voltageVad. It should be noted, however, that when the pulsation frequency ofthe first output voltage Vad increases and pulsation suppression by thenoise filter 140 starts, the first analog signal A1k no longer pulsatesin association with the reference voltage Vref. Hence, the digitalconversion accuracy is deteriorated. An abnormality determination inthis state is made by monitoring the smoothed power-supply monitorsignal Ma1 at the end of the multi-channel A-to-D converter 124A or bymonitoring the unsmoothed power-supply monitor signal Mb1 at the end ofthe multi-channel A-to-D converter 124B.

Also, the second analog signal A2j is inputted into the multi-channelA-to-D converter 124B as a measure, in the case of the second analogsensor 105, to effectively utilize the characteristics thereof that adetection output itself of the sensor does not vary even when an averagevalue or a pulsation amplitude of the first output voltage Vad variesand hence accurate digital conversion can be performed by smoothing thepulsation component as long as an average value of the reference voltageVref of the multi-channel A-to-D converter 124B maintains apredetermined degree of accuracy.

It should be noted, however, that because the digital conversionaccuracy is deteriorated when the pulsation average value of the firstoutput voltage Vad varies, an abnormality determination in this state ismade depending on magnitude of the pulsation component by monitoring thesmoothed power-supply monitor signal Ma1 at the end of the multi-channelA-to-D converter 124A or by monitoring the unsmoothed power-supplymonitor signal Mb1 at the end of the multi-channel A-to-D converter124B.

Referring to FIG. 10, Step 1002 following Step 401 is a step in whichthe digital conversion values of the smoothed power-supply monitorsignal Ma1, the unsmoothed power-supply monitor signal Mb1, the secondpower-supply monitor signal Mb2, and the third power-supply monitorsignal Mb3 are stored in first through fourth FIFO tables formed of theshift registers SRGi=SRG0, SRG1, SRG2, and SRG3, respectively.Subsequent Step 403 a is a step in which the moving average value iscalculated for the latest predetermined number of digital conversionvalues stored in each of the shift registers SRG2 and SRG3 stored inStep 1002 by dividing a sum of each shift register by the number ofadditions. Herein, subsequent Step 403 b is omitted and advancement ismade to Step 404.

Step 1005 that functions when a determination of YES is made in Step 404is a step in which a maximum deviation, which is a deviation between amaximum value and a minimum value, is calculated for any one of thelatest predetermined number of digital conversion values stored in therespective shift registers SRG0, SRG1, SRG2, and SRG3 in Step 1002. Itis, however, preferable to perform probable statistical processing, bywhich actual maximum value and minimum value are discarded and adeviation between the second largest value and the second smallest valueis found to be the maximum deviation.

Subsequent Step 1006 a is a determination step in which a determinationis made as to whether the maximum deviation calculated in Step 1005 isexcessively large or not by comparison with a determination threshold ofthe maximum deviation set in advance for any one of the digitalconversion values of the smoothed power-supply monitor signal Ma1, theunsmoothed power-supply monitor signal Mb1, the second power-supplymonitor signal Mb2, and the third power-supply monitor signal Mb3. Whenthe maximum deviation is excessively large, a determination of YES ismade and advancement is made to Step 407 a. When the maximum deviationis normal, a determination of NO is made and advancement is made to Step406 b. Herein, a step block 1008 made up of Step 1005 through Step 407 bcorresponds to an abnormality determination portion.

Step 1009 that functions when a determination of NO is made in Step 404or Step 406 b or subsequent to Step 407 b is a step that corresponds toan abnormality determination subject update portion that sequentiallyupdates the shift register number selected in Step 1005 from SRG0 toSRG1, from SRG1 to SRG2, from SRG2 to SRG3, and from SRG3 to SRG0.

The above description is silent about a correction of a digitalconversion error accompanying a variation of the average value of thefirst output voltage Vad for the second analog sensor 105. However, thefirst output voltage Vad is calibrated to be a predetermined outputvoltage at a reference environmental temperature in an inspection stagewhen the product is shipped. Further, it is preferable to store and savestandard data of average correlation characteristics of a nearbytemperature of the constant-voltage power supply 110 with respect to thefirst output voltage Vad empirically measured in advance using a largenumber of product samples in a non-volatile data memory, which is apartial region of the program memory. It is preferable that theconstant-voltage power supply 110 is provided with an unillustratedtemperature sensor, so that the micro-processor 121 estimates a value ofthe first output voltage Vad at a current temperature by monitoring anearby temperature of the constant-voltage power supply 110 while theelectronic control device 100C is in operation. Then, themicro-processor 121 calculates, correction coefficient K=(estimatedvoltage/calibrated first output voltage), and obtains a digitalconversion value calibrated by D2j/K obtained by dividing the digitalconversion value D2j of the second analog signal A2j by the correctioncoefficient K.

It is difficult to determine whether a value of the first output voltageVad is within the target allowable error unless there is anotherreference voltage that can be believed to have a higher degree ofaccuracy. However, in the event of any abnormality in a feedback controlsystem that performs constant-voltage control, an abnormalitydetermination can be made by monitoring the smoothed power-supplymonitor signal or the unsmoothed power-supply monitor signal Mb1described above.

In the event of an abnormal state in which the value of the first outputvoltage Vad significantly deviates from the target allowable error, theaverage values of the digital conversion values of the second and thirdpower-supply monitor signals Mb2 and M3 take an abnormal value. It istherefore possible to estimate which one of the first output voltageVad, the second output voltage Vcp, and the third output voltage Vif isabnormal according to the majority logic.

As is obvious from the description above, an electronic control deviceof the third embodiment is the electronic control device 100C including:the constant-voltage power supply 110 having one or more than oneconstant-voltage control circuit portions that distributes and feeds ordivides and feeds the first output voltage Vad, the second outputvoltage Vcp, or the third output voltage Vif, each of which is fed to adifferent subject, by the input power-supply voltage Vb fed from theoutside power supply 101; and the main control circuit portion 120Chaving the micro-processor 121, the program memory 122C, and the RAMmemory 123 fed by the second output voltage Vcp, and the multi-channelA-to-D converter 124C fed by the first output voltage Vad, all of whichcooperate to drive the electronic load group 107 under control inresponse to an operation condition of the switch sensor group 106 andthe analog sensor group 108.

The multi-channel A-to-D converter 124C generates a digital output inproportion to a ratio (Vin/Vref) of the reference voltage Vref appliedto the reference voltage terminal and the input signal voltage Vin and,when the ratio is 1, generates a maximum digital output, Dout=2^(n)−1,according to an n-bit resolution, where n is a predetermined number.

The first output voltage Vad having the highest degree of accuracy amongthe multiple output voltages is applied to the reference voltageterminal as the reference voltage Vref and the smoothed power-supplymonitor signal Ma1 used as the power-supply monitor voltage is inputtedas one of input signal voltages Vin of the multi-channel A-to-Dconverter 124C, or a voltage is applied to the reference voltageterminal from the first output voltage Vad as the reference voltage Vrefby suppressing a pulsation component via the reference power-supplyfilter 129 and the unsmoothed power-supply monitor signal Mb1 to be usedas the power-supply monitor voltage is inputted as one of the inputsignal voltages Vin of the multi-channel A-to-D converter 124C.

The smoothed power-supply monitor signal Ma1 is a smoothed voltageobtained from a divided voltage of the first output voltage Vad bysuppressing a pulsation component via the first power-supply filter 119,and a dividing ratio of the divided voltage is set so that the smoothedvoltage takes a value not greater than a lowest value of a pulsation ofthe reference voltage Vref. The unsmoothed power-supply monitor signalMb1 is a divided voltage of the first output voltage Vad and a dividingratio of the divided voltage is set so that the divided voltage takes avalue not greater than the lowest value of the pulsation of thereference voltage Vref.

The micro-processor 121 cooperates with the program memory 122C andperiodically inputs a digital conversion value of one of the smoothedpower-supply monitor signal Ma1 and the unsmoothed power-supply monitorsignal Mb1, respectively, into the shift registers SRG0 and SRG1 formedof the RAM memory 123 to calculate a maximum deviation, which is adeviation between a maximum value and a minimum value of the latestpredetermined number of digital conversion values, and determines anabnormality in the constant-voltage power supply 110 in a case where thecalculated maximum deviation exceeds a predetermined threshold value.

The electronic control device 100C may be configured in such a mannerthat one or both of the second output voltage Vcp and the third outputvoltage Vif are generated, respectively, by second and thirdconstant-voltage control circuit portions separated from theconstant-voltage control circuit portion that generates the first outputvoltage Vad.

Herein, as one of the input signal voltages Vin of the multi-channelA-to-D converter 124C, at least one of the second power-supply monitorsignal Mb2 and the third power-supply monitor signal Mb3 to be used asthe power-supply monitor voltage is inputted.

The second power-supply monitor signal Mb2 takes a value of the secondoutput voltage Vcp and a maximum value of the second output voltage Vcptakes a value not greater than a minimum value of the reference voltageVref.

The third power-supply monitor signal Mb3 is a divided voltage of thethird output voltage Vif that feeds the input interface circuit 125 andthe output interface circuit 126 provided to the main control circuitportion 120C, and a dividing ratio of the divided voltage is set so thata maximum value of the divided voltage takes a value not greater thanthe minimum value of the reference voltage Vref.

The micro-processor 121 cooperates with the program memory 122C andperiodically inputs the digital conversion value of one of the secondpower-supply monitor signal Mb2 and the third power-supply monitorsignal Mb3, respectively, into the shift registers SRG2 and SRG3 formedof the RAM memory 123 to calculate an average value of the latestpredetermined number of digital conversion values and a maximumdeviation, which is a deviation between a maximum value and a minimumvalue of the latest predetermined number of digital conversion values,and determines an abnormality in the constant-voltage power supply 110in a case where the calculated maximum deviation or both of thecalculated maximum deviation and the calculated average value exceedrespective predetermined threshold values or predetermined band values.

According to the second characteristics of the invention describedabove, of the multiple output voltages generated by the constant-voltagepower supply 110, the first output voltage Vad having the highest degreeof accuracy or a smoothed voltage thereof is inputted as the referencevoltage Vref and at least one of the second output voltage Vcp and thethird output voltage Vif is inputted as the power-supply monitorvoltage, so that the presence or absence of an abnormality in theconstant-voltage power supply 110 is determined by calculating anaverage value or a maximum deviation of the pulsation of the digitalconversion values of the power-supply monitor voltage.

Hence, there is a characteristic that when the first output voltage Vadis determined as being normal, by inputting the first output voltage Vadhaving a high degree of accuracy as the reference voltage Vref, itbecomes possible to determine in a reliable manner the presence orabsence of an abnormality or the presence or absence of a pulsationvariation, which is a sign of the occurrence of an abnormality, inoutput voltages other than the first output voltage Vad.

The micro-processor 121 cooperates with the program memory 122C andperiodically makes an abnormality determination alternately for at leastone of the smoothed power-supply monitor signal Ma1 and the unsmoothedpower-supply monitor signal Mb1 and at least one of the secondpower-supply monitor signal Mb2 and the third power-supply monitorsignal Mb3, so that more than one abnormality determination is not madein a same control flow.

According to the third characteristics of the invention described above,the abnormality determination processing for the power-supply monitorsignals of multiple types is performed in a time-dividing manner.

Hence, there is a characteristic that because more than one abnormalitydetermination is not made in the same computation cycle, it becomespossible to make an abnormality determination for multiple outputvoltages one by one by lessening a burden of high speed control on themicro-processor 121.

The multi-channel A-to-D converter 124C is divided to multiplemulti-channel A-to-D converters 124A and 124B. The first output voltageVad is applied to the reference terminal of one multi-channel A-to-Dconverter 124A as the reference voltage Vref, and a voltage is appliedfrom the first output voltage Vad to the reference terminal of the othermulti-channel A-to-D converter 124B as the reference voltage Vref bysuppressing a pulsation component via the reference power-supply filter129. An input signal obtained from the first analog sensor 104 isinputted into an analog input terminal of the multi-channel A-to-Dconverter 124A with a priority as a first analog signal A1k, and aninput signal obtained from the second analog sensor 105 is inputted intoan analog input terminal of the other multi-channel A-to-D converter124B with a priority as a second input signal A2j.

According to the seventh characteristics of the invention describedabove, the first analog signal from the first analog sensor 104, adetection signal voltage of which varies in proportion to a value of thefirst output voltage Vad, is inputted into the multi-channel A-to-Dconverter 124A operating on a stabilized control voltage by theconstant-voltage power supply 110 used as the reference voltage Vref,and the second analog signal from the second analog sensor 105, adetection signal voltage of which remains stable even when a value ofthe first output voltage Vad varies, is inputted into the othermulti-channel A-to-D converter 124B operating on a voltage obtained fromthe first output voltage Vad by the constant-voltage power supply 110 bysmoothing a pulsation component and used as the reference voltage Vref.

Hence, there is a characteristic that even in a case where the firstoutput voltage Vad is in a normal state and has a low-frequencypulsation, both of the first and second analog sensors 104 and 105 canperform accurate digital conversion. In a case where there are more thanor less than necessary first and second analog sensors 104 and 105 andthere are more than or less than necessary inputs and outputs for eitherthe multi-channel A-to-D converter 124A or 124B, either one of the firstand second analog sensors 104 and 105, whichever has the largerdetection signal voltage and does not require a high-accurate digitalconversion value, can input signals into either one of the multi-channelA-to-D converters 124A and 124B. Hence, it can be suppressed that theinputs to the multi-channel A-to-D converts 124A and 124B as a whole areexcessive, which is an uneconomical operation.

While the first through third embodiments of the invention have beendescribed, it is understood that the respective embodiments can becombined without any restriction and the respective embodiments can bemodified or omitted as the need arises within the scope of theinvention.

Various modifications and alterations of this invention will be apparentto those skilled in the art without departing from the scope and spiritof this invention, and it should be understood that this is not limitedto the illustrative embodiments set forth herein.

What is claimed is:
 1. An electronic control device, comprising: aconstant-voltage power supply having a constant-voltage control circuitportion that operates in one of manners so as to distribute and feed andto divide and feed one of a first output voltage and a second outputvoltage among multiple output voltages, each of which is fed to adifferent subject, by an input power-supply voltage fed from an outsidepower supply; and a main control circuit portion including amulti-channel A-to-D converter fed by the first output voltage having ahighest degree of accuracy among the multiple output voltages, and amicro-processor, a program memory, and a RAM memory fed by the secondoutput voltage, all of which cooperate to drive an electronic load groupunder control in response to an operation condition of a switch sensorgroup and an analog sensor group, wherein: the multi-channel A-to-Dconverter generates a digital output in proportion to a ratio of areference voltage applied to a reference voltage terminal and an inputsignal voltage and, when the ratio is 1, generates a maximum digitaloutput, 2^(n)−1, according to an n-bit resolution, where n is apredetermined number; the reference voltage terminal is fed in one ofthe following manners in which, the first output voltage is applied tothe reference voltage terminal as the reference voltage and a smoothedpower-supply monitor signal to be used as a power-supply monitor voltageis inputted as one of input signal voltages of the multi-channel A-to-Dconverter, and a voltage is applied to the reference voltage terminalfrom the first output voltage as the reference voltage by suppressing apulsation component via a reference power-supply filter and anunsmoothed power-supply monitor signal to be used as the power-supplymonitor voltage is inputted as one of the input signal voltages of themulti-channel A-to-D converter; the smoothed power-supply monitor signalis a smoothed voltage obtained from a divided voltage of the firstoutput voltage by suppressing a pulsation component via a firstpower-supply filter, and a dividing ratio of the divided voltage is setso that the smoothed voltage takes a value not greater than a lowestvalue of a pulsation of the reference voltage; the unsmoothedpower-supply monitor signal is a divided voltage of the first outputvoltage and a dividing ratio of the divided voltage is set so that thedivided voltage takes a value not greater than the lowest value of thepulsation of the reference voltage; and the micro-processor cooperateswith the program memory and periodically inputs a digital conversionvalue of one of the smoothed power-supply monitor signal and theunsmoothed power-supply monitor signal into a shift register formed ofthe RAM memory to calculate a maximum deviation, which is a deviationbetween a maximum value and a minimum value of a latest predeterminednumber of digital conversion values, and determines an abnormality inthe constant-voltage power supply in a case where the calculated maximumdeviation exceeds a predetermined threshold value.
 2. The electroniccontrol device according to claim 1, wherein: one or both of the secondoutput voltage and a third output voltage among the multiple outputvoltages are generated, respectively, by a second or thirdconstant-voltage control circuit portion separated from theconstant-voltage control circuit portion that generates the first outputvoltage; as one of the input signal voltages of the multi-channel A-to-Dconverter, at least one of a second power-supply monitor signal and athird power-supply monitor signal to be used as the power-supply monitorvoltage is inputted; the second power-supply monitor signal takes avalue of the second output voltage and a maximum value of the secondoutput voltage takes a value not greater than a minimum value of thereference voltage; the third power-supply monitor signal is a dividedvoltage of the third output voltage that feeds an input interfacecircuit and an output interface circuit provided to the main controlcircuit portion, and a dividing ratio of the divided voltage is set sothat a maximum value of the divided voltage takes a value not greaterthan the minimum value of the reference voltage; and the micro-processorcooperates with the program memory and periodically inputs the digitalconversion value of one of the second power-supply monitor signal andthe third power-supply monitor signal into the shift register formed ofthe RAM memory to calculate an average value of a latest predeterminednumber of digital conversion values and a maximum deviation, which is adeviation between a maximum value and a minimum value of the latestpredetermined number of digital conversion values, and determines anabnormality in the constant-voltage power supply in one of cases wherethe calculated maximum deviation exceeds one of a predeterminedthreshold value and a predetermined band value and where both of thecalculated maximum deviation and the calculated average value exceed oneof respective predetermined threshold values and predetermined bandvalues.
 3. The electronic control device according to claim 2, wherein:the micro-processor cooperates with the program memory and periodicallymakes an abnormality determination alternately for at least one of thesmoothed power-supply monitor signal and the unsmoothed power-supplymonitor signal and at least one of the second power-supply monitorsignal and the third power-supply monitor signal, so that more than oneabnormality determination is not made in a same control flow.
 4. Theelectronic control device according to claim 1, wherein: the firstoutput voltage is applied to the reference voltage terminal as thereference voltage and the smoothed power-supply monitor signal to beused as the power-supply monitor voltage is inputted as one of the inputsignal voltages of the multi-channel A-to-D converter; the analog sensorgroup includes a first analog sensor that operates on the first outputvoltage as a power supply, a detection signal voltage of which as asensor varies in proportion to a value of the first output voltage, anda second analog sensor that operates on one of the input power-supplyvoltage and the first output voltage as a power supply, a detectionsignal voltage of which as a sensor is not influenced by a pulsationvariation of the first output voltage; input circuits of the firstanalog sensor and the second analog sensor include bypass capacitorsthat suppress a foreign high-frequency noise in a band of several MHz totens MHz, and noise filters that suppress a noise component of tens Hzto several KHz or higher generated in the input circuits are connectedto the input circuits; of the noise filters, at least the noise filterconnected to the first analog sensor is a low-pass filter having a firstbreak frequency; and the first power-supply filter is a low-pass filterthat smoothes a pulsation component of tens Hz to tens KHz or higher,which are pulsation frequencies when the first output voltage is in anabnormal state, and has a second break frequency lower than the firstbreak frequency.
 5. The electronic control device according to claim 4,wherein: the micro-processor cooperates with the program memory andperiodically inputs a digital conversion value of a second analogsignal, which is at least one of signals of the second analog sensor,into the shift register formed of the RAM memory to calculate a movingaverage value, which is an average value of a latest predeterminednumber of digital conversion values, and specifies the calculated movingaverage value as a digital conversion value for the second analogsignal.
 6. The electronic control device according to claim 1, wherein:a voltage is applied from the first output voltage to the referencevoltage terminal as the reference voltage by suppressing a pulsationcomponent via the reference power-supply filter, and the unsmoothedpower-supply monitor signal to be used as the power-supply monitorvoltage is inputted as one of the input signal voltages of themulti-channel A-to-D converter; the analog sensor group includes a firstanalog sensor that operates on the first output voltage as a powersupply, a detection signal voltage of which as a sensor varies inproportion to a value of the first output voltage, and a second analogsensor that operates on one of the input power-supply voltage and thefirst output voltage as a power supply, a detection signal voltage ofwhich as a sensor is not influenced by a pulsation variation of thefirst output voltage; input circuits of the first analog sensor and thesecond analog sensor include bypass capacitors that suppress a foreignhigh-frequency noise in a band of several MHz to tens MHz, and noisefilters that suppress a noise component of tens Hz to several KHz orhigher generated in the input circuits are connected to the inputcircuits; of the noise filters, at least the noise filter connected tothe first analog sensor is a low-pass filter having a first breakfrequency; and the reference power-supply filter is a low-pass filterthat smoothes a pulsation component of tens Hz to tens KHz or higher,which are pulsation frequencies when the first output voltage is in anabnormal state, and has a break frequency as high as the first breakfrequency.
 7. The electronic control device according to claim 1,wherein: the first output voltage is applied to the reference voltageterminal as the reference voltage and the smoothed power-supply monitorsignal to be used as the power-supply monitor voltage is inputted as oneof the input signal voltages of the multi-channel A-to-D converter; theanalog sensor group includes a first analog sensor that operates on thefirst output voltage as a power supply, a detection signal voltage ofwhich as a sensor varies in proportion to a value of the first outputvoltage, and a second analog sensor that operates on one of the inputpower-supply voltage and the first output voltage as a power supply, adetection signal voltage of which as a sensor is not influenced by apulsation variation of the first output voltage; input circuits of thefirst analog sensor and the second analog sensor include bypasscapacitors that suppress a foreign high-frequency noise in a band ofseveral MHz to tens MHz, and noise filters that suppress a noisecomponent of tens Hz to several KHz or higher generated in the inputcircuits are connected to the input circuits; of the noise filters, atleast the noise filter connected to the first analog sensor is alow-pass filter having a first break frequency; the first power-supplyfilter is a low-pass filter that smoothes a pulsation component of tensHz to tens KHz or higher, which are pulsation frequencies when the firstoutput voltage is in an abnormal state, and has a second break frequencylower than the first break frequency; the multi-channel A-to-D converteris divided to multiple multi-channel A-to-D converters, so that thefirst output voltage is applied to a reference terminal of onemulti-channel A-to-D converter as the reference voltage and a voltage isapplied from the first output voltage to a reference terminal of theother multi-channel A-to-D converter as the reference voltage bysuppressing a pulsation component via the reference power-supply filter;an input signal obtained from the first analog sensor is inputted intoan analog input terminal of the one multi-channel A-to-D converter witha priority as a first analog signal; and an input signal obtained fromthe second analog sensor is inputted into an analog input terminal ofthe other multi-channel A-to-D converter with a priority as a secondanalog signal.